Mechanically Interfacing with Biology via Piezoelectric Nanowires

Collectively, cells can perform incredibly complex tasks. Their function allows us to interact with the world, fight disease and repair the materials that make us. The ability to control this behaviour could lead to significant advances in areas such as regenerative medicine, tissue engineering and bio-mimetic materials. However, interfacing directly with cells to dictate their behaviour is far from trivial. The chemical pathways and mechanisms that typically regulate cell function have been devised over millions of years of evolution, resulting in fiercely complex and finely balanced systems. Interfering with these schemes rarely succeeds. Interestingly, a new and emerging field of research known as mechanobiology may offer a solution to this problem. This describes the phenomenon whereby cellular systems are exceptionally sensitive to their mechanical environment, i.e., the function and behaviour of cells can be regulated by the physical properties of their surroundings and the forces that they experience. As an example, human stem cells grown on a soft substrate are likely to differentiate into fat cells, while growing those same stem cells on a rigid substrate will lead to the formation of bone cells. The challenge of controlling cell function is then shifted to the challenge of controlling the mechanical properties of cell surroundings. In this context, piezoelectric materials are ideal candidates for tools within mechanobiology, given their ability to both detect and apply small forces. By combining piezoelectric materials with a grid of electrodes, similar to that found on the touch screen of a phone, a 'touch screen for cells' can be created. Cells growing on this device will exert a force on the piezoelectric material, causing it to develop some electric charge. This charge can then be detected with some degree of spatial resolution using the grid of electrodes. Furthermore, via the same grid of electrodes, individual areas of the piezoelectric interface...